The HLA class II gene cluster plays an essential role in immune activation by presenting processed antigens to various lymphoid cell types of the immune system. This role is not only functional during the body's normal defense against invading pathogens, but also during an inappropriate attack on self tissues causing autoimmune diseases. In type I diabetes (IDDM or insulin dependent diabetes mellitus) this autoimmune attack is on the islet cells of the pancreas whose function is to secrete insulin and regulate the body's glucose metabolism. Not all of the hundreds of possible HLA genes are associated with this inappropriate autoimmune attack. Indeed, only two of the 25 known HLA DQB1 genes, namely DQB1 0201 and 0302, are highly associated with the disease in caucasian populations while the DQB1 0303 allele is associated with increased risk for IDDM in the Asian population. In addition, another of these genes, DQB1 0602, has the ability to suppress this greater risk of contracting diabetes when present as part of the heterozygote inheritance with 0302. The rarer DQB1 0202 allele has not been studied with respect to diabetes risk assessment. However, since its DNA sequence is identical to the DQB1 0201 sequence in the region of antigen binding, it is thought to impart the same increased risk as the DQB1 0201 allele. The increased risk of contracting type I diabetes can be as high as 200 fold for people who have inherited both the DQB1 0201 and 0302 genes (see, J. Nepom, Diabetic Reviews 1:93 (1993)).
U.S. Pat. No. 5,039,606 "Diagnostic Probe for Diabetes Type I Predisposition" filed Oct. 29, 1987 describes a probe sequence which purportedly was specifically reactive with the DQB1 0302 sequences. However, subsequent HLA sequencing (see, Marsh and Bodmer, Tissue Antigens, 45:258-280 (1995), incorporated by reference herein) has revealed that the probe is not specific to DQB1 0302 allele. In fact, the disclosed probe reacts with nine of the twenty-five known DQB1 alleles, namely 0302, 03032, 0305, 0401, 0402, 05031, 05032, 06011, and 06012.
Accordingly, what is needed in the art are compositions and methods for specifically detecting all of the high risk alleles: DQB1 0201, 0202, 0302, 0303. Additionally, what is needed are compositions and methods for specifically detecting the risk reducing DQB1 allele 0602. More particularly, what is needed are compositions and methods to specifically and simultaneously detect the DQB1 alleles 0201, 0202, 0302, 0303, and 0602 under the uniform low-temperature assay conditions which are desirable for high volume clinical testing. Quite surprisingly, the present invention provides these and other advantages.